I know this sort question pop ups frequently, but I was hoping to get answer more target it to my situation, so I hope no one minds me dredging up an old topic.

I'm looking for a 3D engine to use to for solo development on a purely hobby basis. I'm not looking make anything remotely releasable, I just fancy learning for learning's sake.

I'm a reasonably proficient C++ programmer, though I haven't done anything game design related for a good 10 years. Have have in past created some basic 2D games using the WINAPI, and played around with DirectX back in version 9. (At push I could create a room with a few crates in it, and move a camera around it)  

I have never used C#, that said, I understand it isn't a great leap for C++ developer to get to grips with, so I'm not against of using it. Though the old die hard C++ dev in me wants to turn my nose up to it

My own research came up with either Unreal or Unity, and was wondering if any one else had experience from similar position could suggest any pitfall I might have in choosing either (or feel free to suggest something different). 

Thanks in advance.

Since you already know C++, Unreal might be a good way to go.  But, I've never used it myself so I dont know what the learning curve is vis-a-vis Unity.  However, since you're just concerned with doing a hobby project and learning, using C++ means you can focus on learning the ins and outs of the engine and what you want to accomplish, rather than learning a new language at the same time.

I do some hobby projects as well, and I would suggest that you try a few engunes and see what you like. I pretty much stick to unity right now, since I'm using C# frequently for other things. (you can use JavaScript as well...).. It sounds like you shouldn't have any trouble learning C# and it is pretty useful if you  want to write other stuff for Windows especially  My knowledge of modern C++ is very limited, and I haven't used Unreal Engine much, so can't give you any advice there

3 hours ago, Ubermeowmix said:

Build your own cross platform sandbox with SDL2 and OpenGL like I have, it's a rough ride but you will learn so much along the way. There is no quick fix or shortcut, get yourself a machete and start hacking away. The more you do the more you will grow, just like everything else you do in life.

While this is certainly a good option especially if the goal is to learn how games and engines work at the lowest levels, it also means quite some time before you can get to a stage where you can get much of the actual game working.  The good thing about starting with an existing engine is that you can learn the high level stuff, and get a game up and running fairly quickly.  You can later focus on the lower level stuff once you know what all the systems should be that need to be in place.

I think it just depends on what aspects the person wants to learn, what they think is fun to build on their own, and whether getting a game working quickly is a priority.